The invention pertains to image acquisition and, particularly, to the acquisition of image data from multiple sources. The invention has application in acquiring images from video cameras and other acquisition devices used in machine vision and in other industrial, research and recreational environments.
It is increasingly common to couple video cameras, and other image acquisition devices, to computers. This has been made possible by increases in computer processing power and storage capacity, as well as by decreases in equipment costs. It is also a consequence of the rise in popularity of the Internet, for which the transmission and display of images is increasingly norm.
Cameras and computers have long been used together in machine vision, which involves the automated analysis of images, typically, to determine characteristics of objects shown in them. It is often employed in automated manufacturing lines, where images of components are analyzed to determine placement and alignment prior to assembly. Machine vision is also used for quality assurance. For example, in the semiconductor device industry, images of chips are analyzed to insure that leads, solder paste and other components do not overrun designated boundaries.
As the machine vision industry has recognized, and consumers are soon to realize, one camera is often not enough. When machine vision is used in manufacturing, for example, it may be desirable to generate multiple simultaneous views of an object. Alternatively, it may be necessary to generate multiple views without moving the camera or the object. Within the consumer domain, web cams and Internet-based videoconferencing are among the applications which are likely to benefit from such uses of multiple cameras.
Notwithstanding the benefits of coupling computers to multiple cameras, no general purpose solutions exist. Some personal computers or workstations are equipped with only a single port capable of receiving high-speed video input streams. That port can be a universal serial bus (USB 2, hereinafter referred to, simply, as xe2x80x9cUSBxe2x80x9d) port, though, it may alternatively be an IEEE 1394-compatible (xe2x80x9cFireWirexe2x80x9d) port. The machine vision industry relies on digital data processors with multiple video ports, however, these xe2x80x9cvision processorsxe2x80x9d can represent an unnecessary expense in situations where the resources of a engineering workstation or personal computer are otherwise available.
In view of the foregoing, an object of this invention is to provide improved methods and apparatus for image acquisition.
A more particular object is to provide such methods and apparatus as permit multiple image acquisition devices to be coupled to a digital data processor.
A still more particular object is to provide such methods and apparatus as permit multiple image acquisition devices to be coupled to a personal computer, workstation or other digital data processor via a single port.
Still another object of the invention is to provide such methods and apparatus as support such coupling through a conventional high-speed serial port, such as a USB port, a FireWire port, or the like.
Still yet further objects of the invention are to provide such methods and apparatus as can be utilized with charge coupled device image acquisition devices.
Yet still further objects of the invention are to provide such methods and apparatus as permit the coupling of multiple video sources to a digital data processor, regardless of whether those sources are image acquisition devices.
These and other objects are met by the invention which provides, in one aspect, a hub that controls the acquisition of images from a plurality of image sources. Image acquisition logic operating within the hub selectively applies a first set of control signals (e.g., xe2x80x9cshutterxe2x80x9d signals) to the sources, causing them to acquire images. The logic applies a second set of control signals (e.g., xe2x80x9creadoutxe2x80x9d signals) to the sources, causing them to output acquired images to the hub. The hub then transmits those images to a host over an isochronous communications medium, e.g., a USB or FireWire bus. As used herein, xe2x80x9cisochronousxe2x80x9d medium refers to a medium that permits creation of a connection (virtual or otherwise) between a source and a destination and that allows allocation of a minimum guaranteed bandwidth for transfer of information between such source and destination, regardless of the existence of other demands for bandwidth allocation or information transfer over that medium. Isochronous also refers to a medium that supports only isochronous transfers or, alternatively, to isochronous phases of a medium that supports isochronous and other types of transfers (e.g., asynchronous). An example of such an isochronous medium is a bus compatible with the aforementioned IEEE 1394 standard.
A hub or other image acquisition control apparatus as described above is advantageous, among other reasons, because it permits multiple image sources to be connected to a personal computer, work station or other host device via a single high-speed port, e.g., a FireWire port or a USB port.
Further aspects of the invention provide a hub (or other image acquisition control apparatus) as described above in which the image sources are cameras or other image acquisition devices and, more particularly, charge coupled device (CCD) image acquisition devices.
Related aspects of the invention provide such a hub for use with CCD or other image acquisition devices of the type that are responsive to a shutter signal for acquiring image data, and to a readout signal for outputting that data. The hub applies the first and second controls signals to such devices in such a way as to cause them to acquire or generate images substantially simultaneously, yet, output them sequentially (or with a desired degree of simultaneity) to the hub.
A hub as described above can operate utilizing instructions issued by the host, which can be for example a personal computer, workstation or other digital data processing device. Such a hub can, further, transfer image data received at its device interfaces substantially immediately to its host interface.
Still further aspects of the invention provide methods of operating hubs or image acquisition control apparatus paralleling the foregoing.
Hubs or image acquisition control apparatus and methods as described above provide numerous advantages in machine vision as well as in other industrial, research, home and recreational environments. Such apparatus and methods take advantage of the storage capabilities of CCD or other image capture devices, permitting multiple images to be acquired, e.g., simultaneously, while minimizing or virtually eliminating the need for buffering image data that are being transferred from the acquisition devices to the host.
These and other aspects of the invention are evident in the drawings and in the description that follows.